Madison Avenue's luxury conversion The Mark had a rough time of it during the downturn?and it had a long way to fall. At one point, billionaire Leonard Blavatnik even promised to pay $150 million for the building's top three floors. But the deal fell through, and the building's other two buyers seemed not much happier about their purchasing decisions. Eventually, all but 10 of the 42 units that were converted to co-ops were converted back into hotel rooms. Still, the building decided to make a comeback attempt, and the first seven re-listings are officially back on the market. The average ask is $5,230/square foot, with the penthouse still hoping for $60 million, or $6,123/square foot. Penthouse photos in the gallery above, plus a handful of other unit floorplans.